Autoranger for soundcards

[Chrisr3521]

OK, so TP12 very low mv dc ~0.090mv. Top of R15 is showing a signal of ~ 0.5v

 

[jan.didden]

Getting closer. Please measure the two points as shown in the attachment.
Same conditions, 1V SE in, 0dB.

Jan

 

[Chrisr3521]

Thanks for this Jan,

So AC test point measures 95mv and DC test point 0.2mv

 

[jan.didden]

That means the problem is in the LTC1968, U4.
Can you verify if all pins are soldered, and that there's no shorts?
It's not easy to check as it's a very small chip.

Jan

 

[Chrisr3521]

Unfortunately I cannot check myself its to small or it seems buy a new one until 2023

 

[Chrisr3521]

I've managed to check continuity to surrounding components and they check out, is there anything else to do.

I'm really disappointed I cannot use this until potentially next year.

 

[Chrisr3521]

OK so luckly found someone with stock on another forum and have had it replaced, does this now look correct?

https://flic.kr/p/2n2B6hV

 

[jan.didden]

OK so luckly found someone with stock on another forum and have had it replaced, does this now look correct?

https://flic.kr/p/2n2B6hV

Yes the numbers looks quite good!
-12dB is ~1/4, 7.37 is about 4 x 1.85.
What is the output level setting you use?
Like 4V?

Jan

 

[Pizzigri]

Hello to the thread!
One question, as I intend to use the Auto Ranger with a Quantasylum QA40x, I could use a BNC as the single ended output of the AR instead of the Neutrik stereo jack? It is not clear. The hole size on the box is not a problem, the way it is connected instead is, I would use a panel mount and wire connections to the PCB - and in that case, an indication of what goes soldered where, would be great. And thank you Jan for all you help!!

 

[jan.didden]

Between (1) and (2), (2) being the BNC gnd. But isolate the BNC from the panel to avoid gnd loops!

Jan

 

[Pizzigri]

Autoranger MkII is a great tool, could be even better.


Thanks for your hard work, Jan. Yes, you are absolutely correct, we can use better op amps with significantly better distortions results. I didn't try OPA1656 yet being quite satisfied with OPA1611 - actually per datasheet it beats OPA1656 having 0.000015% (-136.5 dB) THD at 1 kHz comparing to 0.000029% (-131dB) for OPA1656. It also has significantly lower voltage noise level at 1.1 nV/sqr Hz at 1 kHz comparing to about 2.9 nV/sqr Hz for OPA1656 (look at the graph in the datasheet for 1 kHz result). Please also note that being unity gain stable, it could eliminate some unpredictable results and be less sensitive to the PBC layout tracing.
But those results are way better anyway comparing to old NE5532 or NE5534.

I use 10 uF MLCC capacitors right on the PS pins of op amps, with 0.033 uF C0G ceramic capacitors in parallel to lower possible noises even deeper.

As a tool, Autoranger MkII can be used with Victor's generator (-140dB at 1 kHz). I would like to thank you guys again for being extremely valuable diyforum members!

Please keep you great work going!

Hello Gordon, I’m curious about the twin t you have there with Vic’s oscillator. Can you give me some construction details on it. I would highly appreciate it.
franco

 

[Pizzigri]

Between (1) and (2), (2) being the BNC gnd. But isolate the BNC from the panel to avoid gnd loops!

Jan

Thank you, can’t wait to start the build!

 

[Chrisr3521]

Yes the numbers looks quite good!
-12dB is ~1/4, 7.37 is about 4 x 1.85.
What is the output level setting you use?
Like 4V?

Jan

Hi Jan,

It was set at 1.5v output, I've since changed it to 0.5 for testing my Motu and Victors oscillator. I'll give it a proper test in the next few days.

 

[jan.didden]

Hello Gordon, I’m curious about the twin t you have there with Vic’s oscillator. Can you give me some construction details on it. I would highly appreciate it.
franco

There a section on single ended and balanced twin T's around the Viktor thread.
Not my design but I designed a PCB for it based on Hammond case with all parts & connectors directly on the board.
It does not harm the performance.

Jan

 

[jan.didden]

Hi Jan,

It was set at 1.5v output, I've since changed it to 0.5 for testing my Motu and Victors oscillator. I'll give it a proper test in the next few d

There a section on single ended and balanced twin T's around the Viktor thread.
Not my design but I designed a PCB for it based on Hammond case with all parts & connectors directly on the board.
It does not harm the performance.

Jan

Example: Viktor's oscillator through balanced twin tee. Twin T has about 70dB attenuation at 1kHz. Clean output.

Jan

 

[Pizzigri]

Example: Viktor's oscillator through balanced twin tee. Twin T has about 70dB attenuation at 1kHz. Clean output.

Jan

That’s impressive Jan, any chance you could let me have a board or gerber with BOM to make myself one?

 

[Chrisr3521]

That’s impressive Jan, any chance you could let me have a board or gerber with BOM to make myself one?

I would be interested as well

 

[jan.didden]

I have 2 balanced boards and more than 10 single-ended boards left. They can go.

Jan

 

[Chrisr3521]

I have 2 balanced boards and more than 10 single-ended boards left. They can go.

Jan

I'll take a balanced pcb Jan please. Pm me with details

 

[Pizzigri]

Hey Jan! I’d love one balanced and one se board!